Load control device



R. L. DAUGHERTY LOAD CONTROL DEVICE 4 Sheets-Sheet 1 Filed June 8. 1959 ATm/zA/EYS 6 l/ rll ,4 9/ 2 m f "0 a2 4 M M wm H I b. w w -m x 5 I a m. 2 a 7 H9 a 0) Mb 6 a /fi w 4 m 2 u m M L 0 w v 6) r 3 6 W 4 w I 7 V H. 0 L a a n 1 M m L, 1 WOW 7 wh 2 M L o w M 6 M V m 0 m 7 m Feb. 12, 1963 R. L. DAUGHERTY 3,077,542

LOAD CONTROL DEVICE Filed June 8, 1959 4 Sheets-Sheet 4 HOUSEHOLD 340 LOADS 1520 HEATING LOA D5 :52 I

HEATING LOADS-52];

INVENTOR.

05527 L. DAUGf/EETY BY 777mm, kemamen, mam and M44, Arrows-Y5 3,677,542 LQAD @UNTR QL DEVECE ilohert L. Daugherty, lleedshurg, Wis, assignor to Robertshaw'Fulton (Controls Qornpany, Richmond, Va., a corporation of Delaware Filed. June 8, i959, Ser. No. 818,728 9 (Ilairns. (Cl. EN -3d) The present invention relates generally to load control devices and, more particularly, to devices for controlling the magnitude of the total electrical load of a domestic or commercial installation.

Although the load control device of the present invention is well suited for use in controlling the total load of an installation employing both electrical heating elements as employed, for example, in space or central heating plants, and conventional household electrical elements, for example, as hot water heaters, stoves, ovens, electrical appliances, lighting fixtures, and the like, the present invention should not be construed as being limited or restricted to this particular application, since it has a wide variety of applications with other types of electrical apparatus.

it is an object of the present invention to provide a load control device for reducing the total load of an electrical installation or system in response to the occurrence of an overload condition in a portion of the system.

it is another object of the present invention to provide a new and improved load control device which maintains the total load of an electrical system below a predetermined peak load value.

it is still another object of the present invention to provide a new and improved load control device for reducing the total load of an electrical installation during selected periods of time of each day.

it is still another object of the present invention to provide a load control device wherein the magnitude of the line voltage supplied to diiierent loads is reduced in response to an overload condition.

it is yet a further object of the present invention to provide a load control device operative in response to an overload condition to render ineffective selected ones of the loads of an electrical system for a predetermined period of time.

it is a further object of the present invention to provide a load control device adapted to reduce an electrically resistive heating load in response to an overload condition in an electrical household load circuit, thereby preventing high total peak loads.

It is yet another object of the present invention to provide in a load control device a new and improved transfer switch which is responsive to an overload condition to reduce the total load of an electrical installation.

It is still a further object of the present invention to provide in a load control device a new and improved transfer switch embodying electromagnetic means which are deenergized when the switch is in its operative positions.

The invention has for anotner object the provision of split bus arrangement for equalizing the load distribution of a single-phase, three-wire system when the circuit connected to the system is overloaded.

The above and other objects are achieved in accordance with the present invention by providing a new and improved load control device adapted to control the total load of an electrical installation in a residential or commercial systen. In one embodiment of the present invention, the magnitude of the line voltage supplied from a single-phase, three-wire supply to electrical loads in a first part of the electrical installation is automatically reduced upon the occurrence of an overload condition in nited States Patent 3,@7'i,l2 Patented Feb. 12,

a second part of the installation. To this end, a detecting means associated with the second part of the installation determines the existence of a current in excess of a predetermincd value and, in response to such current, operates a transfer switch which decreases the amount of voltage supplied to the first part of the installation. lfter the current in the second part of the installation falls below the predetermined value, the detecting means an emailcally operates the switch to apply the full line voltage to the loads in the first part of the installation. A split bus arrangement is employed to provide for distribution of the loads, thereby minimizing the possibility of overload in any one phase.

In another embodiment of the present invention, selected ones or" the loads in the first part of the installation are sequentially rendered ineiiect-ive under the control of a timer apparatus for a predetermined period. of time in response to an overload condition in the second part of the installation. A detecting means is associated with the second part of the installation but, instead of controlling a transfer switch, the latter detecting means controls the timer apparatus which operates sequentially to render ineffective selected ones of the loads in the first part of the installation, thereby to reduce the total load in the first part of the installation to a fraction of the normal load without rendering all of the loads completely in operative during the period of operation of the timer apparatus. if at the end of the period of operation of the timer apparatus the overload condition in the second part of the installation has subsided, all of the loa s in the first part of the installation are again rendered effective.

in each of the described embodiments, provision is made for operating the transfer switch and the timer apparatus, respectively, independently of the detecting means during certain periods of time during each day. Thus, the consumer may limit his power consumption during there periods, i.e., leak load hours, in order to take advantage of lower rates which are offered in many areas for off peak power.

As indicated above, in the first embodiment of the present invention, a new and improved transfer switch is utilized to change the magnitude of the voltage supplied to the loads in the iirst part of the installation. The switch is of the over-center type and employs suitable electromagnetic means which are momentarily energized to move the switch between its operative positions, the electromagnetic means being deenergized when the switch is in its operative position. The switch is further characterized by having pairs of its contacts biased together, independently of other pairs of contacts, to assure good electrical conduction between the switch contacts.

The invention, both as to its organization and manner of operation, together with further objects and advantages, will be best understood by reference to the following detailed description considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic view of a load control device which is characterized by the features of the present invention and which includes a transfer switch shown in its inoperative condition;

FIG. 2 is a fragmentary schematic view, similar to PEG. 1, but shows the transfer switch in its operative condition;

PEG. 3 is a top plan view of the transfer switch employed in the circuit shown in FlGS. 1 and 2;

FIG. 4 is a sectional view taken along a line substantially corresponding to line 4-4 of FIG. 3 with certain parts being broken away to facilitate the illustration;

FIG. 5 is a fragmentary, sectional view taken along a line substantially corresponding to line 5-5 of FIG. 3;

FIG. 6 is a fragmentary sectional view taken along a line substantially corresponding to line 6--6 of FIG. 4-;

FIG. 7 is an enlarged, fragmentary sectional view taken along a line substantially corresponding to line 7-7 of FIG.

FIG. 8 is a schematic view of another embodiment of the load control device of FIG. 1; and

FIG. 9 is a chart depicting the timing cycle of a timer apparatus used in the embodiment of the invention shown in FIG. 8.

Referring now to the drawings, there is illustrated a load control device for regulating the load in an electrical system. A first embodiment of the load control device is illustrated in FIGS. 1 through 7 while a second embodiment of the load control device is illustrated in FIG. 8. In both of these embodiments the load control device functions to regulate and maintain the total load of the electrical system below a predetermined value.

The use of electricity for heating homes and other buildings is gaining increasing favor because of the many advantages offered with respect to cleanliness and quietness of operation, low cost of maintenance and the like. Even more widespread use of electricity has been hindered by the somewhat higher cost of power than with other heating systems such as gas or oil. Therefore, systems or devices for decreasing the power costs are in great demand and it is to the solution of this problem that the present invention is devoted. The load control device of the present invention is of particular benefit to consumers in those areas where power is offered at a reduced rate for controlled heating, i.e., reduced rates are in effect whenever the load is maintained below a predetermined level similar to the night-time or off peak water heating rates offered by many power companies.

Considering now the first embodiment of the invention illustrated in FIGS. 1 through 7, the load control device is there identified generally by reference numeral 10. The load control device 1%, as shown, is used to regulate or control the total load of an electrical system 11 which is energized from an electrical supply identified generally by reference numeral 12. The electrical supply 12 is shown as being a conventional single-phase, three-wire system including power conductors 14- and 16 and a ground conductor 18, the voltage between the power conductors 14 and 16 being 220 volts and the voltage between each of the power conductors 14 and 15 and the ground conductor, being 110 volts, as is well known. Although the load control device It has many applications, it is illustrated and described, for convenience, as used in an electrical system 11 for supplying 220 volt and/or 110 volt power to conventional household loads 20, which loads may include, for example, stoves, ovens, washing machines, dryers, lighting fixtures, and the like. The 220 volt loads are, of course, supplied with power from conductors 14- and 16 while the 110 volt loads are preferably distributed substantially equally between wire 14 and the ground conductor 18 and wire 16 and ground conductor 18. The system is also illustrated as normally supplying 220 volt power to electric heating loads 21 which may include space heaters and/or a central heating system for a home or building. The electrical loads 21 are illustrated as being of two types 21a and 21b, both of which are normally energized by 220 volts supplied from conductors 14 ano 16 through a split bus arrangement described more fully below.

Briefly, the load control device 10 is operative to reduce the magnitude of voltage supplied to the electrical heating loads 21, whenever the total household load 20 reaches a predetermined value. 'matically reducing the voltage applied across the electrical heating loads from 220 volts to 110 volts whenever the power consumed by the household loads 29 exceeds the predetermined value. It should be understood that since the household loads comprise stoves, ovens, kitchen and the like appliances, and electrical lighting apparatus, which are intermittently used throughout the day, the total load of the household circuit at any particular time is This is accomplished by auto simply the sum of the individual loads of the different electrical appliances or devices in use. Because it is not customary to use all of the household load simultaneously, the total load of the household circuit is generally somewhat less than the maximum possible household load. However, occasionally a great many of the household loads are operated thereby to cause the household circuit to draw more electrical energy from the electrical supply 12 than is desired.

In electrical installations, like the system 11, where both electrical heating loads and electrical househoid loads are employed, it is necessary to maintain the total load for the household and heating circuits below a pre-- determined value in order to take advantage of the lower rates available in many areas. Thus, the load control device It is operative to maintain the total load of the installation below the predetermined value by reducing the power requirements of the heating circuit whenever the power drawn by the household circuit exceeds a particular level. It will be appreciated that during the daylight hours when the greatest use of household apparatus is made, heating requirements are at a minimum so that the voltage to the heating load 21 can be reduced without inconvenience to the occupant of the building whereas if the voltage supplied to the household electrical appliance were reduced, the appliance might not function properly. In accordance with the present invention, the voltage applied across the heating loads 21 is reduced when necessary to keep the total load below the predetermined level and, at the same time, the voltage or voltages applied to the household loads 20 are maintained.

Considering now the embodiment of the invention shown in FIG. 1 in detail, the power conductors 14 and 16 of the electrical supply system 12 are electrically connected to the household loads 29 through a current transformer 22 while the ground conductor 18 is electrically connected directly to selected ones of the loads 21). Accordingly, as shown, the loads 20 connected between the power conductors 1d and 16 are energized with 220 volts while the loads connected between the ground conductor 13 and either of the power conductors 14- or 16 are energized with 110' volts. However, irrespective of the connection of the household loads to the supply 12, the current flow through the power conductors 14 and 16 provides an accurate indication of the electrical energy supplied to all of the household loads. The current transformer 22, which is energized by the current flow through the two power conductors 14 and 16, is of conventional construction and includes a core formed by upper and lower legs 24 and 26 interconnected, respectively, by outer legs 28 and 30 and an intermediate or center leg 32. It further includes primary windings 34 and 38 respectively wound about the outer legs 28 and 30 and a secondary winding 35 wound upon the center leg 32. As shown, the power conductor 14 is electrically connected to one end of the primary widing 34 which is electrically connected at its other end to the household load 28 by a conductor 35. In similar manner, the power conductor 16 is electrically connected to one end of the primary winding 38 which has its other end electrically connected to the house hold loads 20- through a conductor 40. The ground conductor 18 of the electrical system 12 is electrically connected to the household loads 26 by a branch line 42. Accordingly, at all times the household loads 2% are supplied with electrical energy from the supply 12 even though the total load of the household circuit may exceed the above-mentioned predetermined value. Moreover, themagnitude of the voltage or voltages applied to the loads 20 does not change assuming, of course, that the voltage from the supply remains constant.

Assuming that the total load of the household circuit is below the predetermined value, the heating loads 21 are electrically connected through a transfer switch to the supply 12 so that these loads are energized by the 220 volts existing between conductors 14 and 16. More specif ically, the power conductor lid is connected to a stationary contact 54a of the transfer switch 69 and to a set of contacts 62 which, when closed, connect the power conductor 14 to a first side of the heating loads Zla. W ten the switch on is in the deenergized condition shown in FIG. 1, the stationary contact 54a is in electrical engagement with a movable contact 54b carried upon an electrically conductive bridge 535 which forms part of the rocker assembly of the transfer switch as, as described hereinafter. The bridge 55 is electrically connected through a conductor 55' to a set of contacts r25 which, when closed, electrically connect the conductor 65 to a first side of the heating loads 215. With the switch dd in deenergized condition, the power conductor 16, which is electrically connected to a stationary contact is electrically connected through a contact Stlb carried upon an electrically conductive bridge 51 on the rocker assembly and through a conductor o l to a second side of both of the heating loads 21a and the heating loads 21b.

It will, therefore, be appreciated that the heating loads Zlla and 21b are both electrically connected through the transfer switch across the power lines lid and 16 so that 220 volts are supplied to the resistive heating loads 21a and Zlb in order to energize these loads whenever thermostats '74 and 8 call for heat. The thermostats '74 and d4 are located in separate electrical circuits, in cluding power sources '72 and 82 and relays 7t? and 8% which respectively control the contacts 62 and as serially connected to heating loads 21a and 211). Of course, the contacts 62 and so may be individually controlled by separate relays, similar to relays ill and hil which are energized by separate thermostats similar to the thermostats 743 and 34. In any event, the resistive heating ele ments 21a and 21!) while energized under the control of the load control device ll; are primarily controlled by the thermostats 74 and $4 and, in fact, will be supplied with 220 volts only in response to a call for heat by the thermostats 74 and 84.

Assuming now that the number of household loads 2% in use is sufficient to draw more total power to the installation than is desired, i.e., the total load of both the household and heating loads exceeds a predetermined value, an excessive amount of current flows through the primary conductors l4 and lit-3 of the electrical supply system 12. This occurrence is referred to hereinafter as an overload condition of the household load circuit. in response to the flow of the excessive amount of cure-nt in the household load circuit, the current transformer 22 provides a signal for moving the transfer switch dll from the position illustratcd in FIG. 1 to the position illustrated in FIG. 2, whereby the electrical connections to the heating loads Ma and 2112 are changed, i.e., the power conductor 1 and the ground conductor 18 are connected across the heating load 21a while the power conductor 16 and the ground conductor are connected across the heating loads 21b.

More specifically, when an overload condition exists in the household load circuit, the current flowing to the household loads 25) through conductors as and it! and through the primary windings 34 and 38 of the current transformer 20, develops a control signal across the secondary winding 2+5. The primary windings 3-4 and 3d are so wound on the legs 2% and 36* that their generated fluxes respectively pass through the center leg 32 in the same direction, i.e., the flux linkages from the windings 34 and 3d are additive in the common center leg 32. As is well known, the amount of flux present in the center leg 32 is directly proportional to the amount of current flowing through the power conductors 36 and lli; Consequently, if the amount of current flowing to the household load circuit is small, the flux in the center leg 32 of the'currcnt transformer 22 is likewise small and, conversely, if the amount of current flowing to the household circuit is large, the flux in the center leg 32 is also large. Hence, whenever the current in the household ti circuit exceeds the predetermined overload value, the flux flow in the center leg 32 of the current transformer 22 also exceeds a predetermined level.

For the purpose of detecting the magnitude of the flux present in the center leg 32. of the current transformer 22 and particularly for determining when an overload ilux exists in the center leg 32, the secondary winding 35' excites a detecting network comprising a rectifier 8d and a condenser 93* connected in parallel with each other. The rectifier 83 rectifies the AC. signal induced in the secondary winding 35 in order to develop across the condenser 96 a DC. voltage having a value directly proportional to the amount of flux in the center leg 32. The DC. voltage developed across the condenser 98 is supplied to a DC. sensitive relay 92 which is accurately set to be operated when this voltage reaches a predetermined level corresponding, of course, to the overload flux. Thus, an overload flu in the leg 32 causes the relay $2 to operate to breal; its contacts 3 and to close its contacts 94. The closing of the contacts M completes an energizing circuit for a solenoid 96 which is mechanically connected to the rocker assembly of the transfer switch through a reciprocable bar 99 and an overcentcr spring arrangement 1%. The energizing circuit for the solenoid 96 includes a power source 98 such as a battery, contacts )4, conductor lllltl, solenoid winding one, conductor 3 .62, pair of contacts we of a position responsive switch 1&5 mechanically linked to the rocker assembly, and a conductor res connected to the power source The solenoid 96 is effective, when energized, to move the transrer switch 69 from the position shown in FIG. 1 wherein the contacts 5[Z-@b, dds-54b are closed, and contacts 52a-52b, saa sss are open to the position shown in FIG. 2 wherein the contacts 52a-52b, docs-56b are closed and the contacts 5da-5tlb, Sea-5 th are opened. As the snap-acting transfer switch dil moves overcenter, the position responsive switch M5 is actuated by the rocker assembly to close its contacts iii? and to open its contacts 1'34, thereby to open the energizing circuit for the solenoid as and, hence, to deenergize the solenoid before the transfer switch till reaches the position shown in FIG. 2. The

tovercenter spring arrangement 1&8, escribed hereinbelow, completes the movement of the transfer switch 69 into the position shown in FIG. 2 independently of the solenoid es.

With the transfer switch as in the position illustrated in RIG. 2, ill) volts are applied across the heating loads 21a and filb. Specifically, the power conductor to continues to be electrically connected to the contacts d2 of the heating load 21a but the contacts 66 are now electrically connected to the power conductor 16 through a circuit including the conductor as, the electrically conductive bridge '55, the contacts 56b--5da, a conductor 15 and the power conductor 16. Furthermore, the second sides of the heating loads 21a and Zllb are no longer connected to the power conductor 16 but are instead connected to the ground conductor 18 through a circuit including the conductor dd, the electrically conductive bridge 51 and the closed contacts 5215-5241. Accordingly, the heating loads 21a are connected between the ground conductor lid and the power conductor 1 while the loads 21!: are connected between the ground conductor l8 and the power conductor 16 and, as a consequence, both of the loads Zia and 211) are supplied with volt power. Since the voltage supplied to both loads is reduced from 220 volts to 110 volts, the heat supplied is reduced to about one-fourth of its former level but, more important, the current flowing through the heating loads 21a and 21b is reduced by one-half so that much less current is drawn from the supply circuit 12. With less current supplied to the heating loads 21, "the total current supplied to both the heating load and household load circuits is maintained below a predetermined level, even though the current requirements of the household load circuit is higher. Thus, by the use of the above described device the user of the system 11 is able to maintain his power consumption below the predetermined level in order to take advantage of the lower power rates.

The load control device it remains operative at least as long as an overload amount of current is supplied to the household load circuit. It will be appreciated that when an overload condition ceases to exist in the household circuit, the current in the conductors as and do de creases with the result that the ilux detected by the secondary Winding 35 also decreases. As a result of the reduction in flux in the center leg 32 of the current transformer 22, the voltage appearing across the D0. sensing relay $2 is reduced. However, because the relay 92 releases at a lower D.C. votage than it picks up, the current in the hoursehold circuit, the flux in the center leg 32, and the DC. voltage across the condenser must fall to approximately 80 percent of the overload current, flux and voltage, respectively, before the relay 92 is deenergized.

This is advantageous since if the relay 5 2- is deenergized H when the overload condition is reached, the load device It} would be repeatedly rendered operative and inoperative as the current in the household circuit vacillated about the overload value. In any event, when the relay 2 is deenergized, the contacts 94 are opened and contacts 93 are closed, thereby opening the energizing circuit for the solenoid g6 at a second point and completing an energization circuit for a solenoid 97 through the power supply 93, cont-acts 93, conductor 110, solenoid winding 97a conductor 112, contacts 1'37, and the conductor 105. The solenoid 97, like the solenoid 96 is mechanically connected to the rocker assembly of the transfer switch 6% through the reciprocable bar 99' and the overcenter spring mechanism 103 and, hence, when this solenoid 97 is energized it is effective to move the transfer switch so from the position illustrated in FIG. 2 back to the original or deenergized position illustrated in FIG. 1. As the transfer switch 61} moves beyond its overcenter position, the switch 105 is actuated by the rocker assembly to close its contacts 104 and to open its contacts Th7, thereby breaking the energization circuit for the solenoid 97. The overcenter spring arrangement ins completes the movement of the transfer switch back to the position shown in FIG. 1 independently of the solenoid 97. In this position, the heating loads are once again energized with 220 volts under the control of the thermostats 74 and 34.

It will be apparent that both of the solenoids 96 and 97 are deenergized when the switch is in either of the positions illustrated in FIGS. 1 and 2 and are only momentarily energized to move the switch beyond its overcenter position. Accordingly, the solenoids 6 and 97 are in inactive condition at all times except when the load control device is initially rendered operative or inoperative.

Another important feature of the present invention resides in the split bus connection of the loads 21 to the power source in a manner which effects distribution of these loads supply under either the low voltage or high voltage condition. Thus, the conductor or bus 14 is connected to one side of the loads 21a in both con ditions of the transfer switch 60 while the other side of these loads is connected to the conductor or bus 16 under the high voltage condition and to the ground conductor or bus 18 under the low voltage condition. The loads 21b, on the other hand, have one side connected to the bus under both conditions of the transfer switch while the other side of these loads is Connected to the bus 14 during the high voltage condition and to the ground conductor or bus 18 duriu g the low voltage condition. Thus, the load is distributed or balanced between conductor 1d and ground conductor 13 and conductor 16 and ground conductor 18.

The load control device it in addition to its function of reducing the total load of the system 11 upon the occurrence of an ovrload in the household load circuit, may

0 also be rendered effective to reduce the total load of the system during selected hours of the day as, for example, during the peak load periods. More specifically, it is known that peak power must be provided by the power companies during certain hours of the day and, thus, quite frequently these companies establish lower rates for offpeak power consumed. Thus, if possible, the consumer should minimize the power consumed during the peak or high rate periods of the day. To this end, a timer mechanism shown diagrammatically and identified by reference numeral 116 is continuously energized by suitable conductors (not shown) leading to the supply 12. The timer mechanism is of conventional construction and, in the interest of simplifying the present description, its detailed structure is neither illustrated nor described. The timer mechanism 11% comprises a suitable actuator (not shown) which is rendered operative during the selected hours of the day, the actuator controlling a suitable mechanical linkage 118 operably connected to the contacts 93 and 94. Thus, during the selected periods of the day, i.e., peak power periods, the timer mechanism 116 closes the contacts 94 whereby the transfer switch 60 moves from the position illustrated in FIG. 1 to the position illustrated in FIG. 2, as described above. As a result, volts is supplied to the heating loads 21a and 21b and the total current supplied to the household and heating circuits is reduced, in the manner previously described. At the end of the peak power period, the timer mechanism 116 closes the contacts 93 and opens the contacts 94, with the result that the transfer switch 63 reverts from the posit-ion illustrated in FIG. 2 to that illustrated in FIG. 1, whereupon 220 volts are again supplied to the heating loads 21!: and 21b.

Considering now the construction details of the transfer switch on, attention is directed to FIGS. 3 through 7. As is there illustrated, the components of the transfer switch 6!) are mounted upon a generally rectangular insulating platform or base 26%. Briefly, the switch (it) comprises a control means, including the above-discussed solenoids 9'6, 97 and position responsive switch 105, and a rocker assembly 2M. movable by the control means between the two operating positions respectively illus trated in FIGS. 1 and 2. The rocker assembly 261 is adapted to establish electrical connection between a plurality of fixed contacts as described above. Six stationary contacts are illustrated in FIG. 3 and these are designated by reference numerals 2630, 203b, 2tl3c, 203d, 203e, and NM. These contacts are similar in construction and each includes an electrically conductive plate 204 suitably secured to the platform 2% by a machine screw 208 (FIG. 5) or the like. Each of the electrically conductive plates 264- supports an electrical terminal or connector 219. In addition, the plates of the contacts 203a, 201%, 203%- and 2tl3d respectively support the stationary contacts Stla, 52a, 54a and 56a referred to above while the plates of contacts 203e and 263 respectively support clamps 222 and 228. The connectors 210 of the contacts Bill-3a, 293b, 203e, 203d, 2tl3e and 293- are respectively connected to the conductors 16, i3, 14, 15, 64 and 65. Each of these connectors comprises a hollow rectangular sleeve 2&9 for receiving one of the male terminals 140, 15a, 16a, 13a, 64a and 55a of the conductors 14, 15, 16, 18, 64 and 65. The sleeve is secured to the plate 2st by a machine screw 2% having its head accommodated within a recess Ztitla in the base 2%. A terminal screw 212 is threaded through a tapped opening in each sleeve in order to lock the terminals within the tubular connectors 21%. To support the fixed contacts 50a, 52a, 54a and 56a in an elevated position upon the plate 2%, each of the latter plates carries a cylindrical terminal support 214 having an axial bore 214a extending partially therethrough for receiving the screw 268 and having a central recess 214!) in its upper end to accommodate a downwardly depending boss on its associated fixed contact. To provide a good electrical and mechanical connection between each of the stationary contacts 50a, 515a, 534a and 56a and its associated support 214, a soldered joint is preferably employed. It will be appreciated that, by the above construction, the conductors 1 l6, l and 18 are respectively connected to the stationary contacts 54a, Silo, 56a and 52a and, further, if desired, these conductors may be easily and quickly detached from the stationary contacts merely by loosening the screws 212.

As briefly described above, the transfer switch on includes a first electrically conductive bridge 51 carrying adjacent its opposed ends the movable contacts 54b and 56b and this switch further includes a second electrically conducting bridge 55 carrying near its opposed ends the contacts 50!; and 52!). Considering the structure of the conductive bridges 5i and 55 in greater detail, the bridge Sit comprises a generally rectangular bar of electrically conductive material such as copper having adjacent each end an opening 2&5. Each of the contacts 5%, 52b, 54%!) and 55b includes a fixed boss, which is received within one of the openings 215 so that the contact faces of the pairs of contacts 5tla-5b, SZa-SZb, 54a-54b and 560-4361) oppose one another. Both a good electrical and mechanical connection is effected between the contacts 50b and 52b and the electrically conductive bridge arm by using a soldered joint to secure the contact bosses within the openings 235. The bridge 55 is identical in construction to the bridge 51 and, to this end, as is shown in FIG. 5, includes a pair of openings like the openings 1215 described above and located respectively adjacent its ends for accommodating bosses on the contacts 5 and 55b, a soldered joint again being used to hold the bosses within these openings.

As is shown in FIG. 3, the bridge 55 is electrically connected to the contact 2 33 by a pigtail conductor 220 which has one of its ends secured to the plate 2% of the contact Ztldf by the clamp 223. A screw 2% is threaded through the clamp 228 and into a tapped opening in the plate 2W- of the contact 2&3 for the purpose of applying clamping pressure to hold the end of the pigtail conductor 22b. The conductor 2% is suitably connected at its other end to the under surface of the conductive bridge 5S. The contact 2%) connects the conductor 22% to a male terminal 65a on the conductor 65, which male terminal 65:; is, of course, accommodated within the female connector 2169 and is secured therein by the screw 21d of the contact 26-31. By this construction, the conductor 65 is electrically connected to both of the movable contacts 54b and 56!; through the conductive bridge 5'5, the pigtail conductor 22b and the plate 2%, and female connector 21% r of the contact 293 In a generally similar manner, the bridge 51 and, hence, its contacts dob and 5215 are electrically connected to the conductor 64. Specifically, a pigtail conductor 22s is secured at one end to the under surface of the bridge 51 and is secured at its other end to the plate can of the contact Ell-3e by a clamp 2.22. Clamping pressure is supplied to the end of the conductor 2126 by tightening a screw 22%. The plate 2% of the contact 2%:36 electrically connects the other end of the conductor 22% to the male terminal of the conductor dd, which connector 640 is disposed within the female connector 21% and is locked therein by the screw 2M.

Considering now the rocker assembly 2% and referring particularly to FIGS. 3 and 5, this assembly comprises a pair of parallel extending, spaced apart insulating bars 23% and 232 respectively interconnected at their ends by a air of conducting arms 236 and 238, the insulating bars 2%, 232, and the arms 236, 23% comprising a generally rectangular frame 231. The frame 231 is pivotally supported from the base 2% for movement between the two operating positions referred to above under the control of the control means. As is best illustrated in FIG. 5, the arms 236 and 5238 are supported for pivotal movement upon a pair of spaced apart Ushaped bracket-s 24b and 242 having their bight portions fixedly secured to the base 2%. Since both of the arms 236 and 258 are identically supported from the brackets are and 242, only the bracket 243. will be described. Specifically, the bracket 2% is secured to the platform 2% by screws 24% and is provided with a pair of legs 24% extending upwardly from the bight portion. At the upper ends of the legs Zebu suitable openings are provided for accommodating a pivot pin 246 which is maintained in assembled relation with the bracket 244} by a pair of lock rings 248 (FIG. 3) seated within annular grooves defined adjacent the opposed ends of the pin 246. The arm. 235 is non-rotatably connected to the pivot pin 246 by a generally flat plate member 259 suitably secured to the under surface of the arms 236 by a pair of rivets 252, the plate 25% having a central deformed portion 256:: for accommodating the pin 246. The arm 23% is non-rotatably supported upon a pivot pin 254 by a plate (not shown) similar to the plate 238. The pivot pin 254- is suitably supported between the upstanding legs 242a of the bracket 242. By this construction the frame 231 is supported for pivotal movement about its longitudinal axis with the arms 236 and 233, being rockable about their midpoints.

As indicated above, the rocker assembly 2% supports the electrically conductive bridges El and 55 and, in accordance with an important feature of the present invention, their contacts 5t)b54b or see-ssh are resiliently urged into engagement with their associated stationary contacts Eda-44: or 52a-56a. As is best shown in FIG. 3, a plurality of somewhat elongated openings 26% are defined near the four corners of the frame 231 and each of these openings is defined by aligned apertures in one of the insulating bars 23% or 232, and in one of the arms 236 and 238. Since the conductive bridges 51 and 55 are identically supported from the frame 23-1 of the rocker assembly 2st, only the support for the bridge 55 will be described in detail. As is best shown in FIG. 3 the two openings 26% at the left side of the frame 231 accommodate a pair of elongated screws 262 having ieir shanks threaded into spaced apart, tapped openings 264- defined in the bridge 55, the screws 262 having enlarged heads 262a seating against the upper surface of the insulating bars 23% and 232. The conductive bridge 55 and the frame 231 are resiliently urged apart by a pair of coil springs 266 wound about the shanks of the screws 262, the ends of the springs ass being seated, respectively, against the lower surface of the arm 23% and the upper surface of the bridge 55, as is clearly shown in FIG. 7. The conductive bridge 51 is supported in a similar manner from the opposite end of the frame 231 and also is resiliently urged away from the arm 23% by a pair of coil springs (not shown) wound around screws 262 threaded into the openings 26% Thus, the conductive bridges 51 and 55 are resiliently suspended beneath the arms 236 and 238 of the rocker assembly 26 1. As a consequence, the movable contacts of each pair Silo-5% or 52b-56b are independently and individually urged into engagement with their associated stationary contacts. More specifically, as is illustrated in FIG. 5, when the rocker assembly Ztll is in the operating position wherein the contact 54b engages the contact 54a, the coil spring 256 is compressed thereby urging the contact 54b downwardly into firm engagement with the stationary contact 54a. Similarly, the contact 5 3!) is urged into positive engagement with the stationary contact 56a by a spring (not shown) acting against the bridge 51. it should be understood that although positive ongagement is simultaneously effected between both of the contact pairs 5411-54-12 and Elia-$65, the pressure applied between the contacts 5 5a and 54b is independent of that applied between the contacts Ella and Ebb, since these pressures are developed by different ones of the coil springs 266. Therefore, variations in the construction of the rocker assembly and the conductive bridges due to manufacturing tolerances or uneven wearing between the pairs 1 1 of contacts 54zz-S4b and tla-5tib do not adversely affect the operation.

The rocker assembly 261 includes an overcenter spring mechanism 269 which, in conjunction with the control means, causes the rocker frame 231 to be moved between its two operating positions, one of which is shown in FIGS. 4 and 5. As best shown in FIGS. 4 and 6, the overcenter spring mechanism 269 comprises a coil spring 1&8 having one end secured to a spring support 270' carried on the frame 231 and having its other end secured to a U-shaped bracket 274- pivotally supported upon the base 206 More specifically, the support 27% is triangular in shape and includes a fiat base flange 27% which is fixedly secured as by rivets 272 (FIG. 3) to the insulating bars 230 and 232. The support 270 is so located on the insulating bars 230 and 232 that a flat lip 27% formed near its upper end is located substantially equidistantly between the two ends and the two sides of the frame 231. As shown, the hooked upper end 108:: of the spring 108 is inserted through an opening 276 in the bracket lip 2.7%, while the lower hooked end ltlfib of the spring 168 is inserted through an opening 278 defined in the center of the bight portion 274a of the U-shaped bracket 274. To provide a snap-acting overcenter operation, the arms 27412 of the bracket 274 are provided with fingers 2740 which extend into openings 280 defined in the upstanding legs of angulated support members 282 secured to the base 206 as, for example, by screws 284-. The fingers 2740 of the bracket 274 loosely fit in the openings 280 to permit the bracket 274 to pivot about a horizontal axis extending through the fingers. The lower end of the spring 1655b is free to move relative to the fingers 274a and, as is Well known, when the lower end of the spring 1081) moves beyond its center position where it is vertically aligned with the spring fingers, the bracket 274 pivots about the supports 282. At this same time, of course, the upper end 108a of the spring 108 moves to the same side of the fingers 274s as the lower end 1081) in a snap-acting manner under the force provided by the spring 108. Since the frame 231 and the suspended conductive bridges 51 and 55 are pivotally supported from the horizontal pins 246 and 254,. the entire rocker assembly 201 follows the movement of the upper end 108a of the spring 108, with the result that the rocker assembly 291 moves from one of its operating positions to the other.

This movement of the spring 168 and, hence, the rocker assembly 201 is obtained by the control means including the pair of solenoids 96 and 97. These solenoids 96 and 97 are selectively energized in the manner indicated above to displace a bar 99 mechanically connected to the overcenter spring arrangement 269. Specifically, the solenoids 96 and 97, as is best shown in FIGS. 3 and 4, are mounted on the base 2% by a plurality of screws 286. Each of the solenoids 96 and 97 includes a laminated core 96b and 97b and an associated energizing winding 96a and 97a. The solenoids 96 and 97 respectively include armaturcs 287 and 283 each of which is connected to the rod 99 by a pivot connection 289 as illustrated in FIGS. 3 and 4. The armature 288 of the solenoid 97 is in its operative position while the armature 287 is in its inoperative or deenergized position. The switch 105 ref rred to above is suitably supported upon the base 263 and includes a switch operating arm lfiSzz (see FIG. 4) carrying a roller /511 engaging the insulating bar 230 so that the solenoids 96 and 5 7 are deenergized as soon as the rocker assembly 201 moves over its center position in the manner described above.

The rocker assembly 2 31 is controlled by the solenoids 96 and 97 through the above-described overcenter spring arrangement 269 and, to this end, the rod 99 is mechanically coupled to the spring 188. Specifically, and as shown in FIGS. 3, 4, and 6, the center portion of the rod 5 9 is divided and bowed to provide a collar 9% encircling the body of the spring 108. Consequently, when either one of the solenoids 96 and 97 is energized to displace the rod 99, the collar construction 99a operates to move the body of the spring 1% either to the left or the right. Incident to this movement of the spring body, the lower end 198 of the spring pivots either to the left or the right until it moves beyond its center position described above. The upper end of the spring 108a is moved in the same direction under the force of the spring 108 with the result that the rocker assembly 291 moves from one of its operating positions to the other. At the same time that the rocker assembly is moving between its operating positions, the switch arm a is operated by the insulating bar 236 to open one of the above-described contacts 104 and 107, thereby to break the energizing circuit for the energized solenoid.

Assuming that the transfer switch so is in the position illustrated in FIGS. 3, 4, and 5, the heating loads 21 are electrically connected to the electrical supply system 12 so that 220 volts is supplied to the heating load circuit. In response to an overload condition in the household load circuit, the current transformer relay 92 becomes effective to close the contacts 94. The closing of the contacts 94 effects the energization of the solenoid 96 to move its associated armature 237 to the left as viewed in FIG. 4, with the result that the collar 99a moves the body of the spring 108 to the left. The movement of the spring 1G8 to the left moves the bight portion 274a or" the bracket 274 to the left. As soon as the bight portion 274:: moves beyond its center position, the spring this moves the rocker assembly 261 in a snap-acting manner into its second operating position, schematically shown in FIG. 2. The movement or" the spring Hi8 and the bracket 274 to the left as viewed in FIG. 4 is limited by a stop 274 (FIG. 3) which may take the form of a screw secured to a flange on one of the support members 232. Immediately after the overcenter spring mechanism 269 takes control of the rocker assembly 261, the contact arm H3551 of the switch 105 operates to open the contacts i 34 and to close the contacts Hi7. The opening of the contacts 1454 deenergizes the relay 96 so that its associated armature 2.37 no longer urges the rod 99 to the left. However, since the spring mechanism 168 is past its overcenter position, the rod 99 is moved to its extreme left position under the sole control of the spring 1%. In this position, neither of the solenoids 96 or $7 is energized since the contacts 194 are opened in the energizing circuit for the solenoid 96 and the contacts 93 are opened in the energizing circuit for the solenoid 97.

When the overload condition in the household load circuit ceases to exist, the current transformer relay 92 operates to close the contacts 93, thereby energizing the solenoid 97. When the solenoid $7 is energized, its asso ciated armature 238 moves to the right as viewed in H6. 4 with the result that the rod 99 and its collar 9941 also move to the right to pivot the lower end of the spring lfit'ib and bracket 274 to the right. Thus, in a manner similar to the action described above, the overccnter spring mechanism 26? returns the rocker assembly in a snap-acting manner, to the operating position, shown in FIGS. 3, 4 and 5, and the switch causes the solenoid 97 to be deenergized. Movement of the spring 198 to the right is limited by engagement of the bracket 274 with a fixed stop 275 in the form of a screw threaded through a flange on the support member 232. The stop screw is locked in position by a not 277.

Considering now the embodiment of the invention illustrated in FIG. 8, the load control device is schematically illustrated therein and is generally identified by refe ence numeral The load control device performs the same general function and operates in the same general manner as the above-described load control device lit, with the exception that instead of changing the magnitude of the voltage supplied to the heating loads when an overload condition occurs in the household circuit, selected ones of the heating loads are sequentially ener- 13 gized and deenergized during predetermined time intervals.

In normal operation, an electrical supply system 312, identical to the above-described supply system 12, supplies electrical energy to an electrical installation comprising a plurality of household loads 32% and a plurality of heating loads 321. The supply system 3A2 specifically cornprises a power conductor 314, a power conductor 316, and a ground conductor 318 for providing either 220 volts or 110 volts in the manner previously described.

The power conductor 314 is connected to selected ones of the household loads 32%) through a conductor ass and through a primary winding 334- wound on an outer leg 328 of a current transformer 322, while the power conductor 315 is connected to selected ones of the household loads 32% through a conductor 34d and through a primary winding 338 wound about the outer leg 33% of the current transformer 322. The ground conductor 31-8 is likewise connected to selected ones of the household loads 32d. ln'addition, the power conductor 314 is also connected to one of the sides of the heating loads 321 through a conductor 301 while the power conductor 316 is connected by a conductor 3&2 to the other sides of the heating loads 321 through pairs or" contacts, collectively referred to as 3633. The contacts 393 are controlled by a plurality of relays 304, which are respectively controlled in the manner previously indicated by a plurality of thermostats 3G5. The thermostats 35. 5 are serially connected through a control governor 366 to a voltage source 3d! which is, in turn, connected to the common sides of the relays 364. Thus, one of the thermostats 3% operates when its measured temperature falls below a predetermined level thereby closing the energizing circuit for its associated relay 3d whereupon the contacts 363 of this relay are closed to supply 220 volts to one of the heating loads In order to detect an overload condition in the household load circuit, the household circuit conductors 336 and 3%, as described above, are connected through the current transformer 322 which is identical in construction to the previously described current transformer 22. A secondary winding 386is wound about the center leg 332, of the core of this transformer. The voltage induced in the secondary winding 3816 is supplied to a parallel circuit comprising a rectifier 388, a capacitor 3% and a DC. sensitive relay 392, this parallel circuit being structurally and functionally identical to the corresponding circuit previously described. Accordingly, in response to an overload condition in the household load circuit, the relay 392 is energized and it remains energized as long as the overload condition persists.

However, in contrast to the previously described FIG. 1 embodiment, the energization of the relay 392 does not efi'ect the operation of a transfer switch but, instead, effects the operation of the control governor 396 comprising those components located within the dotted lines. Another difference in the FIG. 8 embodiment resides in the fact that the overload control device 3% and specifically the control governor 306 is rendered operative for a predetermined time following the overload even though the overload condition may have been remedied during this predetermined time. In further contrast to the FIG. 1 embodiment and as indicated above, selected ones of the heating loads 321 are sequentially rendered operative for selective periods during the predetermined time, thereby reducing the current drawn by the heating load circuit and, thus, reducing the current demands on the power supply system 312.

In. response to an overload condition in the household load circuit, the relay 392 is operated in. the manner indicated above to close a pair of contacts 394. The closure of the contacts 394 completes an energizing circuit for an electric timer motor 4th) from the power source 307, through a conductor 492, through a common relay conductor 404, through the closed contacts 3%, through a conductor 4%, through a pair of closed contacts 418a controlled by a timer earn 418, through a conductor 468, through the timer motor 4%, and through a conductor 4% which is electrically connected to the power source 343-7. The energization of the timer motor drives its associated timer cams did, 412, 414, and are in order to respectively control associated contacts 410a, 412a, 414a and 416a which are serially connected with the thermostatic control relays 3ti4. The motor still also drives the timer cam 418 that controls contacts 418a and 4181; located in the energizing circuit for the timer motor 4%. It will thus be appreciated that selected ones of the heating loads 321 are sequentially rendered operative and inoperative during the timing cycle of the timer motor 4%. The cams 410, 412, did and 416 are so oriented on their driving shaft and are so shaped that they are effective to close their associated contacts in sequence and for approximately equal time intervals. Thus, since four cams are illustrated, during the first quarter of the timing cycle, one-fourth of the heating loads 321 (those controlled by contacts dliia) are energized while the remaining three-fourths are inoperative. During the second portion of the timing cycle, a second one-fourth of the heating loads (those controlled by contacts 412a) are energized while the balance of the heating loads are inoperative, and so on.

Returning now to the operation of the timer motor 4%, when the control governor 336 is operative, the timer motor contacts assume the positions indicated in solid lines in FIG. 8. As shown, the timer motor cams 41%, 412, 414 and 415 are so related that the contacts 410a, 412a, 414a and 416:: are closed while the motor earn 418 is so related that the contacts 413a are closed and the contacts 4131') are opened. However, when the relay 392 operates to complete the above-described energizing circuit for the timer motor 4th), the timer motor cams are, 412, 414, 416 and 418 are driven to cause the contacts 412a, 414a, 416a and llda to open and the contacts 41812 to close, the contacts 419:; remaining closed under the control of the cam 41%? as will be observed from the timing chart shown in PEG. 9. The closing of the contacts 41812 completes a holding circuit for the timer motor 490 from the power source 31W, through the conductor 402, through a conductor 42%, through the closed contacts 413 through the conductor 493, through the timer motor ilth and through the conductor 4% connected to the power source 3&7. Hence, the timer motor 4% is energized through its own contacts 41% entirely independently of the relay contacts 394, and, hence, entirely independently of the current transformer 322 which is responsive to the overload condition in the household load circuit. Accordingly, even though the overload condition in the household load circuit is remedied immediately after the timer motor 4&0 commences its operation, the control governor 3% continues to control the sequential operation of the heating loads 321 for the duration of the timer cycle of the timer motor 4'99.

The opening of the pairs of contacts 412a, dlda, and at the start of the timing cycle renders the heating loads 321d through 321k inoperative during the first portion of the timing cycle since the energizing circuit for their associated control relays 394 are opened. The contacts 41641, which remain closed during the first portion of the cycle, condition the heating loads 3221a, 32% and 3251c for operation under the control of the thermostats 385a, Sildb and Eo -Sc respectively. More particularly, in response to a call for heat by all of the thermostats 305a, 335 5 and 355s, electrical energizing circuits are completed for the associated relays Fiii ia, 3434b, and 3M0 from the power source 3W7, through the common conductor 422, through a conductor 42 through the contacts iltla, through a common conductor 426, through the individual thermostats Soda, 3555b and 3tl5c, through the individual relays 394a, 394b, Bid-ts, through the common conductor id i, through the conductor 597, and through t e conductor connected to the power source The close their contacts thereby supplying the heating loads respectively w'h 220 volts from the previously described above. Since a, 321!) and 3210 rendered opera- 3 e under control of the thermostats 3%!) and was, it is possible during the first portion of the timing cycle at one or more of the thermostats 3%551, 3&5!) and Will not cal for heat.

At the end of the first portion of the timing cycle, for example, after a thirty-second time interval, the timer motor cam operates to open the contacts ildo and the timer motor cam 412 simultaneously operates to close the contacts lTiZa. Accordingly, the heating loads 321a, 3131b and 3210 are rendered inoperative under the control or" the timer cam era for the balance of the timing cycle and the heating loads 32in, 32h: and 321 are conditioned by the timer cam 412'. for operation under the control of their associated thermostats 335d, 3ll5e and Btifiy' for the second portion of the timer cycle. Of course, the heating loads 321g through 321k remain inoperative under the control of the timer cams 414 and 4-1-5 for the second portion of the timing cycle. The operation then continues in an obvious manner for the third and fourth portions of the cycle. These portions need not be equal although this is the preferred operation.

At the end of the timing cycle, for example, after a total lapse of two minutes, the timer cam operates to close the contact 418a and to open the contacts 413]). The opening of the contacts 518b breaks the holding circuit for the timer motor 4% while the closing of the contacts 418a conditions the timer motor energizing circuit so that it will be completed by the contacts in response to the next overload in the household circuit. Accordingly, the operation of the control governor 3% is again controlled by the current transformer 322. Assuming that the overload condition in the household load circuit has been remedied sometime during the timer cycle, it will be observed that at the end of this cycle the contacts 394 are opened, the timer motor 4th) is decnergized and the control governor ass is inoperative. Thus, at the end of the timing cycle, heating loads 321a through 321k are returned to the exclusive control of their associated thermostats through Eildk. Accordingly, if all of the thermostats call for heat, all of the heating loads 321:: through 321k are simultaneously supplied with 220 volts from the supply system 312. The heating loads 321a and 321k all remain operative under the control of their respective thermostats until an overload condition again occurs in the household load circuit and the con trol governor is again rendered operative.

In the event that the overload condition continues to exist in the household load circuit at the end of the timer cycle, the above described energizing circuit for the timer motor is completed when the contacts 413a are closed by the cam 413. Thus, the motor remains energized and the earn 418 operates to simultaneously open the contacts 413a and close the contacts 41311 to complete the above-described holding circuit for the motor 4%. Accordingly, the control governor is rendered operative again to sequentially render operative the heating loads and the above described operation is therefore repeated for another complete cycle. The cyclic operation of the control governor 3% is thus successively repeated as long as the overload condition exists in the household load circuit.

in certain domestic or commercial installations, it is usually necessary to continually supply heat for a particular purpose even though an overload condition exists within the household circuits. To this end, a heating load, for example, the heating load 32bit, is operated entirely independently of the control governor 396. More specifically, the control relay 364m is not energized through the control governor 3th? but is energized exclusively through its associated thermostat 335122 by a circuit including the power source 3%), the common conductor 422, a conductor 442, the thermostat 3tie'm, the control relay 364m, the common conductor 494, and the con ductor ltlfc. connected to the power source 367. Of course, if continued heating or the like is not required in the installation, the thermostat 3l5m can alternatively be connected to the common conductor 44% instead of to the conductor 442, thereby permitting this thermostat to be controlled by the control governor 3%.

As previously discussed in connection with the FIG. I embodiment of the present invention, the load control device 3% may be provided with a timer mechanism 45% for assuring that the total installation load will be maintained below a predetermined value during periods of peak power demands each day. Thus, by using the control governor to limit the heating load during these peak power periods each day, advantage may be taken of the lower power rates. Specifically, the timer mechanism 45d includes a timer motor (not shown) suitably energized by the supply system 312 and further includes a pair of contacts 451 controlled by a suitable cam (not shown) driven by the timer motor (not shown). The contacts 451 are electrically shunted across the conductors 484 and 4% by a pair of conductors 452 and 454. It will be appreciated that the contacts 451 are also connected in parallel with contacts 394 of the current transformer relay 392 and, thus, they control the operation of the control governor. Hence, during the selected hours of the day, the contacts 45?. are closed, thereby to close the energizing circuit for the timer motor 4% including the power source 3W, the conductor :89, the timer motor 4%, the conductor 4%, the contacts 418a, the conductor 466, conductor 452, the timer mechanism contacts 451, the conductor 4-54, the conductor 464, and the conductor hi2 connected to the power source 397. The operation of the timer motor 4% is identical to that described above and will be obvious. The contacts 451 remain closed during the peak power periods and, accordingly, the energizing and holding circuits function continuously to energize the timer motor 4% so that the cyclic operation of the control governor 306 is repeated.

From the foregoing description it will be appreciated that selected ones of the heating loads are rendered operative and inoperative in order to reduce the heating load power requirements of the installation 311, either by operation of the current transformer 322 in response to an overload condition or by operation of the timer mechanism 454 during the peak power periods.

While there has been described an illustrative embodiment of the invention, it will be understood that various modifications may be made therein which are within the true spirit and scope of the invention as defined in the appended claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is: l. In an electrical system for controlling the distribution of power between a plurality of electrical loads of ditlerent priority connected in first and second circuits, means connecting said circuits to a common power source, and means responsive to an overload condition in said. first circuit for reducing the total ffective load of the electrical loads in said second circuit as long as said overload condition exists thereby to reduce the eitective peak load on the power source during the time that the overload condition exists.

2. in an electrical control apparatus for plurality of electrical devices connected in first an second circuits, terminal means adapted to be connected to voltage source, circuit means into connecting said terminal means and said first and second circuits, and means responsive to an overload condition in said first circuit for sequentially disconnecting from said voltage source different ones of the electrical devices in said second circuit for 17 predetermined periods of time so that less than all of the electrical devices are connected to said voltage source at any one time following the occurrence of the overload condition.

3. In an electrical control apparatus for a plurality of electrical devices connected in first and second circuits, terminal means adapted to be connected to a voltage source, circuit means interconnecting said terminal means and said first and second circuits, means responsive to an overload condition in said first circuit for sequentially disconnecting from said voltage source different ones of the electrical devices in said second circuit so that less than all of the electrical devices are connected to said voltage source at any time following the occurrence of an overload condition, and including a timer motor means associated with said disconnecting means and energized by the occurrence of said overload condition.

4. The apparatus of claim 3 wherein said timer motor means includes a plurality of cam means for individually controlling the electrical devices during the spaced predetermined periods of time.

5. In an electrical control apparatus for a plurality of electrical devices, terminal means adapted to be connected to a voltage source, circuit means interconnecting said terminal means and said electrical devices, means responsive to an overload condition, means controlled by said responsive means for sequentially disconnecting from and connecting to said voltage source selected ones of the electrical devices to obviate said overload condition, and control means independent of said disconnecting means and included in said circuit means for rendering certain ones of said electrical devices electrically inoperative during a predetermined period of each day.

6. In an electrical control apparatus for a plurality of electrical devices connected in first and second circuits, terminal means adapted to be connected to a voltage source, circuit means interconnecting said terminal means and said first and second circuits, means responsive to an overload condition in said first circuit for sequentially disconnecting selected ones of said electrical devices in said second circuit from said voltage source for predetermined periods of time, and control means in said second circuit operable independently of said disconnecting means for electrically disconnecting certain ones of said electrical devices in said second circuit from said voltage source during a predetermined period of each day.

7. In an electrical control apparatus for a plurality of electrical devices connected in first and second load circuits of different priority, terminal means adapted to be connected to a voltage source, circuit means interconnecting said terminal means and said first and second circuit, and means responsive to an overload condition in a said circuit of first priority for reducing the magnitude of voltage to the electrical devices in said circuit of second priority thereby to reduce the peak load of the devices in both the first and second circuits at the terminal means.

8. In a system for controlling the delivery of power to a plurality of loads from a three-wire source including first and second conductors and a neutral conductor, the combination of means connecting the power source to the loads and including a switch selectively operable between a first position wherein high voltage from the source is applied across the loads and a second position wherein low voltage from the source is applied across the loads, said connecting means including a first circuit for connecting the first conductor of the source to one side of a first group of loads irrespective of the switch position and a second circuit for connecting the second conductor of the source to one side of a second group of loads irrespective of the switch position, said connecting means including circuit means for connecting the other side of the first group of loads to the second conductor when the switch is in said first position and for connecting said other side of the'first group of loads to the neutral conductor when the switch is in its second position, and said connectin means further including circuit means for connecting the side of the second group of loads to which the second conductor. is not connected to the first conductor when the switch is in its first position and for connecting the side of said second group of loads to which the second conductor is not connected to the neutral conductor when the switch is in said second position.

9. In a system for controlling the delivery of power to a plurality of loads from a three-wire source including first and second conductors and a neutral conductor, the combination of means connecting the power source to the loads, said connecting means includinga switch operable in response to an overload on said source for movement from a first position wherein high voltage from the source is applied across the loads to a second position wherein low voltage from the source is applied across the loads, said connecting means including a Split bus arrangement for connecting the voltage existing between the first and second conductors across said loads when the switch is in the first position and for connecting the voltage between the first conductor and the neutral con ductor across one group of loads and the voltage between the second conductor and the neutral conductor across another group of loads when the switch is in the second position.

References Cited in the file of this patent UNITED STATES PATENTS 2,372,102 Mahnke Mar. 20, 1945 2,614,189 Mosely Oct. 14, 1952 2,769,924 Beery Nov. 6, 1956 2,874,310 Young Feb. 17, 1959 2,923,831 Wallene Feb. 2, 1960 

3. IN AN ELECTRICAL CONTROL APPARATUS FOR A PLURALITY OF ELECTRICAL DEVICES CONNECTED IN FIRST AND SECOND CIRCUITS, TERMINAL MEANS ADAPTED TO BE CONNECTED TO A VOLTAGE SOURCE, CIRCUIT MEANS INTERCONNECTING SAID TERMINAL MEANS AND SAID FIRST AND SECOND CIRCUITS, MEANS RESPONSIVE TO AN OVERLOAD CONDITION IN SAID FIRST CIRCUIT FOR SEQUENTIALLY DISCONNECTING FROM SAID VOLTAGE SOURCE DIFFERENT ONES OF THE ELECTRICAL DEVICES IN SAID SECOND CIRCUIT SO THAT LESS THAN ALL OF THE ELECTRICAL DEVICES ARE CONNECTED TO SAID VOLTAGE SOURCE AT ANY TIME FOLLOWING THE OCCURRENCE OF AN OVERLOAD CONDITION, AND INCLUDING A TIMER MOTOR MEANS ASSOCIATED WITH SAID DISCONNECTING MEANS AND ENERGIZED BY THE OCCURRENCE OF SAID OVERLOAD CONDITION. 